Bug 1765423 - Make tooltips look nicer with default window themes. r=dao

For that, make the Windows rounded-rect code apply to tooltips as well.

Differential Revision: https://phabricator.services.mozilla.com/D145327

toolkit/themes/windows/global/tooltip.css

@@ -19,11 +19,25 @@ tooltip {
 }
 
 @media (-moz-windows-default-theme) {
-  /* We use Window / WindowText instead on the default theme because the
-     default yellowish styles are somewhat ugly */
   tooltip {
-    background-color: Window;
+    /* These are the same colors as --menu-background-color and co., but we
-    color: WindowText;
+       can't quite use them because the default tooltip is native anonymous and
+       doesn't inherit from the root. */
+    background-color: #f9f9fb;
+    color: #15141a;
+    border-color: #cfcfd8;
+
+    /* Force a rounded-rect dropshadow to appear. */
+    -moz-window-shadow: cliprounded;
+    border-radius: 4px;
+  }
+
+  @media (prefers-color-scheme: dark) {
+    tooltip {
+      background-color: #2b2a33;
+      color: #fbfbfe;
+      border-color: #5b5b66;
+    }
   }
 }
 

widget/windows/nsWindow.cpp

@@ -1816,7 +1816,8 @@ static bool ShouldHaveRoundedMenuDropShadow(nsWindow* aWindow) {
 // XXX this is apparently still needed in Windows 7 and later
 void nsWindow::ClearThemeRegion() {
   if (mWindowType == eWindowType_popup &&
-      (mPopupType == ePopupTypeMenu || mPopupType == ePopupTypePanel) &&
+      (mPopupType == ePopupTypeTooltip || mPopupType == ePopupTypeMenu ||
+       mPopupType == ePopupTypePanel) &&
       ShouldHaveRoundedMenuDropShadow(this)) {
     SetWindowRgn(mWnd, nullptr, false);
   } else if (!HasGlass() &&
@@ -1830,9 +1831,9 @@ void nsWindow::ClearThemeRegion() {
 void nsWindow::SetThemeRegion() {
   // Clip the window to the rounded rect area of the popup if needed.
   if (mWindowType == eWindowType_popup &&
-      (mPopupType == ePopupTypeMenu || mPopupType == ePopupTypePanel)) {
+      (mPopupType == ePopupTypeTooltip || mPopupType == ePopupTypeMenu ||
-    nsView* view = nsView::GetViewFor(this);
+       mPopupType == ePopupTypePanel)) {
-    if (view) {
+    if (nsView* view = nsView::GetViewFor(this)) {
       LayoutDeviceIntSize size =
           nsLayoutUtils::GetBorderRadiusForMenuDropShadow(view->GetFrame());
       if (size.width || size.height) {